Refractories bonded with aluminides,nickelides,or titanides

ABSTRACT

DENSE COMPOSITIONS HAVING A GRAIN SIZE SMALLER THAN 10 MICRONS AND CONTAINING FROM 10 TO 80 VOLUME PERCENT OF A WEAR-RESISTANT MATERIAL SELECTED FROM THE GROUP CONSISTING OF (A) ALUMINUM NITRIDE, (B) TANTALUM NITRIDE, (C) MIXTURES OF (A) AND (B), AND (D) A REFRACTORY OXIDE OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ZIRCONIUM, HAFNIUM, TITANIUM, CHROMIUM, BERYLLIUM, ZINC, CALCIUM, THORIUM, BARIUM, STRONTIUM, SILICON, THE RARE EARTH METALS, AND MIXTURES THEREOF; 15 TO 80 VOLUME PERCENT OF A METALLINE SELECTED FROM THE GROUP CONSISTING OF TITANIUM CARBIDE, TITANIUM NITRIDE, ZIRCONIUM CARBIDE, ZIRCONIUM NITRIDE, TANTALUM CARBIDE, NIOBIUM CARBIDE, NIOBIUM NITRIDE, AND MIXTURES THEREOF; AND 5 TO 35 VOLUME PERCENT OF AN INTERMETALLIC SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM NICKELIDE, TANTALUM NICKELIDE, ZIRCONIUM, NICKELIDE, NIUBIUM NICKELIDE, COBALT, ALUMINIDE, COBALT TITANIDE, IRON ALUMINIDE, IRON TITANIDE, NICKEL ALUMINIDE, NICKEL TITANIDE, TUNGSTEN ALUMINIDE, MOLYBDENUM ALUMINIDE, NIOBIUM ALUMINIDE, TANTALUM ALUMINIDE, TITANIUM ALUMINIDE, ZIRCONIUM ALUMINIDE, AND MIXTURES THEREOF ARE (1) EFFECTIVE FOR CUTTING TOOLS FOR HIGH SPEED MACHINING AND (2) RESISTANT TO OXIDATION.

3,676,161 DES, OR

y 1972 P. c. YATES' REFRACTORIES BONDED WITH ALUMINIDES, NICKELI TITA ESF l :1 Marc 5, 1969 WEAR RESISTANT MATERIAL /V\A/V W v M Q "W N 7INTERIETALLIO /V\, fif NETALLINE INVENTOR PAUL C.YATES fi g 5 MS/(MATTORNEY United States Patent 01 ice 3,675,161 Patented July 11, 1972US. Cl. 106-55 14 Claims ABSTRACT OF THE DISCLOSURE Dense compositionshaving a grain size smaller than 10 microns and containing from 10 to 80volume percent of a wear-resistant material selected from the groupconsisting of (a) aluminum nitride, (b) tantalum nitride, '(c) mixturesof (a) and (b), and (d) a refractory oxideof an element selected fromthe group consisting of magnesium, zirconium, hafnium, titanium,chromium, beryllium, zinc, calcium, thorium, barium, strontium, silicon,the rare earth metals, and mixtures thereof; 15 to 80 volume percent ofa metalline selected from the group consisting of titanium carbide,titanium nitride, zirconium carbide, zirconium nitride, tantalumcarbide, niobium carbide, nio bium nitride, and mixtures thereof; and 5to 35 volume percent of an intermetallic selected from the groupconsisting of molybdenum nickelide, tantalum nickelide, zirconium,nickelide, niobium, nickelide, cobalt, aluminide, cobalt titanide, ironaluminide, iron titanide, nickel aluminide, nickel titanide, tungstenaluminide, molybdenum aluminide, niobium aluminide, tantalum aluminide,titanium aluminide, zirconium aluminide, and mixtures thereof are (1)effective for cutting tools for high speed machining and (2) resistantto oxidation.

SUMMARY OF THE INVENTION It has been discovered that particularcompositions of aluminum nitride, tantalum nitride or refractory oxides(other than aluminum oxide) and certain carbides and nitrides bondedwith an intermetallic are useful for making cutting tips having unusualproperties. These compositions can be used to produce a cutting tip withan unusual combination of hardness and strength and one which is veryresistant to wear and thermal shock. In addition the dense compositionsof this invention are useful as wear resistant, oxidation-resistant andchemical-resistant materials of construction.

This invention is directed to such dense compositions which have anaverage grain size smaller than 10 microns and are composed to twointerpenetrating three-dimensional networks; one network consistingessentially of a wear-resistant material selected from the groupconsisting of:

(a) aluminum nitride;

(b) tantalum nitride;

(0) mixtures of aluminum nitride and tantalum nitride;

and

(d) a refractory oxide an element selected from the the other networkconsisting essentially of a metalline selected from the group consistingof:

titanium carbide, titanium nitride, zirconium carbide, zirconiumnitride, tantalum carbide, niobium carbide, niobium nitride, andmixtures thereof;

and an intermetallic selected from the group consisting of:

molybdenum nickelide, tantalum nickelide, zirconium nickelide, niobiumnickelide, cobalt aluminide, cobalt titanide,

iron aluminide,

iron titanide,

nickel aluminide, nickel titanide, tungsten aluminide, molybdenumaluminide, niobium aluminide, tantalum aluminide, titanium aluminide,zirconium aluminide, and mixtures thereof;

the wear-resistant material being present in an amount ranging from 10to volume percent; the metalline being present in an amount ranging from15 to 80 volume percent; and the intermetallic being present inan amountranging from '5 to 35 volume percent, with the limitation that thevolume percent of the metalline must not be less than the volume percentof the intermetallic.

Surprisingly these composition demonstrate exceptional advantages oversimilar compositions consisting of closely related compounds and overcompositions of these same compounds in different amounts. As a resultof their exceptional properties the compositions of this invention areuseful in cutting and milling ferrous alloys even at very high cuttingspeeds.

DESCRIPTION OF DRAWING DESCRIPTION OF THE INVENTION Components Therefractory compositions of this invention consist essentially of awear-resistant material, a metalline, and an intermetallic.

(a) Wear-resistant material-The Wear resistant materials arecommercially available as fine powders. Although minus 80 mesh powders(US. Standard Sieve Series) may be used to prepare compositions of theinvention, minus 200 mesh powders are preferred and minus 325 meshpowders most preferred. Aluminum nitride powders are available fromConsolidated Astronautics, Inc. or Materials for Industry; tantalumnitride powders from Cerac, Inc.; and the refractory oxide powders maybe obtained from sources such as Zirconium Corporation, BerylliumCorporation, Foote Minerals, and Materials for Industry.

The wear resistant material is selected from the group consisting of:

(a) aluminum nitride;

(b) tantalum nitride;

(c) mixtures of aluminum nitride and tantalum nitride;

and

(d) a refractory oxide of an element selected from the group consistingof magnesium, zirconium, hafnium, titanium, chromium, beryllium, zinc,calcium, thorium, barium, strontium, silicon, the rare earth metals, andmixtures thereof,

and is present in the composition in amounts ranging from 10 to 80volume percent. Compositions containing less than 10 volume percent donot possess adequate wear resistance, and above 80 volume percent thecompositions are excessively brittle.

The wear-resistant material is preferably present in amounts rangingfrom 10 to 50 volume percent and more preferably from 15 to 30 volumepercent, since these amounts give rise to compositions having anexcellent balance of wear resistance, strength and toughness.

(b) Carbides or nitrides (metalline).The metalline compounds are used inthe compositions of this invention in amounts ranging from 15 to 80volume percent and are selected from the group consisting of titaniumcarbide, titanium nitride, zirconium carbide, zirconium nitride,tantalum carbide, niobium carbide, niobium nitride, and mixturesthereof.

When zirconium carbide or zirconium nitride is used, it may contain asmall amount of hafnium carbide or nitride (i.e., 1% t by weight,usually about 2%), which is normally present as an impurity in technicalgrades of zirconium compounds.

Preferred amounts of metalline range from 30 to 60 volume percent andmost preferred amounts range from 45 to 55 volume percent. These amountscontribute most effectively to properties such as hardness and wearresistance in the compositions of this invention.

The metalline can be obtained commercially or can be synthesized bymethods well known to the art. The metallines should preferably have aparticle size of less than 5 microns and more preferably less than 2microns. If the starting material is appreciably larger than 5 micronsin particle size it can be pre-ground to reduce its size to that whichis acceptable. Of course the milling of the components of thisinvention, which is carried out to obtain a high degree of homogeneity,will result in some comminution of the metalline and the other startingcomponents.

Titanium nitride, titanium carbide, zirconium nitride, and zirconiumcarbide are preferred for use in the compositions of this invention asthey are readily available, result in compositions which have anexcellent balance of physical properties, and demonstrate greateffectiveness when used to cut or mill ferrous alloys. The mostpreferred metalline is titanium nitride.

(c) Intermetallic.The intermetallics suitable for use in this inventionare selected from the group consisting of molybdenum nickelide, tantalumnickelide, zirconium nickelide, niobium nickelide, iron aluminide, irontitanide, cobalt aluminide, tungsten aluminide, molybdenum aluminide,niobium aluminide, titanium aluminide, zirconium aluminide, and mixturesthereof. The intermetallic is present in amounts ranging from 5 to 35percent. At least five volume percent is necessary in order to provideany significant bonding in the body and amounts greater than this giverise to additional strength and toughness although 4 decreased wearresistance. Above 35 volume percent little further improvement instrength is obtained, but the wear resistance is decreased considerably.

The intermetallic is preferably present in amounts ranging from 15 to 30volume percent, and more preferably from 20 to 30 volume percent, sincethese amounts result in strong compositions without adversely affectingwear resistance.

When zirconium aluminide or zirconium titanide is used, it may containthe usual amounts of hafnium, i.e., from 1% to 5% by weight.

The most preferred intermetallics are molybdenum nickelide, ironaluminide, cobalt aluminide, and nickel aluminide, because they are themost ductile of the refractory intermetallic binders used in thecompositions of the invention.

Aluminides of nickel, molybdenum, and niobium available from Cerac,Inc.; iron aluminide from Shieldalloy Corp.; iron titanide fromShieldalloy Corp. or Foote Mineral Co.; and nickel titanide from MetalHydrides, Inc. may be used. Also the intermetallic compounds can besynthesized in situ by mixing together the correct ratio of elements inthe powder from which the dense bodies of the invention are made.

The intermetallics can be synthesized by melting together thestoichiometric ratio of the components in an inert refractory cruciblein a vacuum furnace. After allowing to cool, the solid billet of theintermetallic can frequently be broken up in a hammer mill and ground toa fine mesh size in a ball mill. Alternatively, a fine powder can beobtained by atomizing the molten intermetallic by the procedures knownto the art for the production of atomized metal powders. Although minus50 mesh powders (US. Standard Sieve Series) may be used to preparecompositions of the invention, minus 200 mesh powders are preferred, andminus 325 mesh most preferred.

The line intermetallic powders prepared as described above can then beincorporated in compositions to be used in fabricating dense bodies ofthe invention,

(d) l-mpurities.The components used in the compositions of thisinvention should be essentially pure. It is desirable to excludeimpurities such as oxygen which would tend to have deleterious effectson the dense compositions of this invention. 7

However, minor amounts of many impurities can be tolerated with noappreciable loss of properties.

Thus, the intermetallic can contain small amounts of metals such astitanium, zirconium, tantalum or niobium as minor impurities, althoughlow melting metals like lead should be excluded. Small amounts ofcarbides other than titanium, zirconium, niobium or tantalum carbide,such as several percent of tungsten carbide, which is sometimes pickedup in grinding, can be present. Even oxygen can be tolerated in smallamounts such as occurs when titanium carbide has been exposed to airresulting in a few percent of titanium oxy-carbide. However, after thepowder components have been milled together and are in a highly reactivestate, oxidation, particularly of the inter-metallic, occurs easily andshould be avoided.

tWhen aluminum nitride is used as the wear-resistant material, it maycontain the amount of A1 0 usually present in commercial grade aluminumnitride, i.e., from 1% to 5% by weight.

Structural characteristics In addition to characterizing the compositionof this invention on the basis of the components discussed above, thecompositions can also be characterized on the basis of their structuralcharacteristics.

(a) Interpenetrating three-dimensional networks-The compositions of thisinvention are characterized as containing two interpenetratingthree-dimensional networks: one of wear-resistant material and one ofintermetallic bonded carbide or nitride. The two networks may beobserved in optical micrographs taken on etched polished surfaces ofcompositions of the invention. Using conventional metallographictechniques and various etches known to those in the art, the contrastbetween the various phases can be brought out and it can be seen thatthere are interpenetrating networks, This can be demonstrated evenfurther using the scanning electron microscope on heavily etchedsurfaces.

While the eifects of the presence of these two networks is notcompletely understood it is believed that they contribute substantiallyto the unusual properties of the compositions of this invention,resulting in compositions much stronger and more impact-resistant thanconventional alumina ceramic cutting tools.

The presence of a continuous phase of the electrically conductingmetalline and intermetallic is apparent from the electrical conductivityof the hot-pressed compositions of this invention. The compositions ofthis invention preferably have a specific electrical resistivity of lessthan about 1 ohm-centimeter, more preferably less than about 25,000micro-ohm-centimeter and most preferably less than 5,000micro-ohm-centimeter. The preferred compositions of this invention, inwhich metalline plus intermetallic amount to 35 volume percent or more,often have a specific electrical resistivity of less than 1000micro-ohm-centimeter.

(b) Thermal coefficients of expansion.Tl1e compositions of thisinvention are also characterized as having two continuousinterpenetrating networks with very similar thermal coefficients ofexpansion. Generally the coefiicient of expansion of the wear-resistantphase as well as the met'alline and intermetallic phase will rangebetween 4 10 and 5 10- inches/inch/ F. at temperatures from roomtemperature up to 1000 F.

As a result of the similarity of these thermal coefficients, cuttingtips of the compositions of this invention are able to undergo extremetemperature change with little or no thermal strain being generatedwithin the composition. The compositions are very resistant to thermalshock both as regards shattering and as regards surface heat cracking.

'(c) Homogeneity and fine-grained structure.The compositions of thisinvention are also characterized as having a fine number average grainsize, smaller than 10 microns and preferably smaller than 5 microns inaverage grain diameter. The number average grain size and thesize'distribution are obtained from enlarged electron micrographs onpolished etched surfaces using an extension of the methods of John E.Hilliard described in Metal Progress, May 1964, pages 99 to .102, and ofR. L. Pullman, described in the Journal of Metals, March 1953, page 447,et seq. The grain size is uniform and homogeneous throughout thecomposition and there is essentially no porosity in the densecompositions of this invention. Distribution of the two co-continuousphases is also uniform and homogeneous, and generally speaking any area100 microns square which is examined microscopically at 1000magnification will appear the same as any other area 100 microns square,within conventional statistical distribution limits.

The fine grain size of the compositions of this invention is of courseat least partly responsible for the continuity of the interpenetratingphases. However it also contributes along with the homogeneity and lowporosity to the abrasion resistance of the compositions of thisinvention. Metal inclusions such as the carbide inclusions in cast ironabrade even the hardest of the metal-bonded, carbide cutting tools.Nevertheless the compositions of this invention are outstandinglyabrasion resistant.

Preparation The preparation of the compositions of this invention isimportant because many of the characteristics of the compositions areachieved as a result of the manner in which theyare prepared. Thus, theuse of fine-grained starting materials and thorough milling of the mixedcomponents are directly related to the fine grain size and uniformhomogeneity of the compositions. Other precautions observed in preparingthe compositions of this invention which have important effects on theproducts are:

(1) the prevention of excessive contamination from grinding media andmoisture or oxygen in the air;

(2) hot-pressing or sintering under conditions which permit the escapeof volatile materials prior to densification;

(3) avoiding undue absorption of carbon from pressing molds by limitingtheir contact under absorptionpromoting conditions;

(4) avoiding excessive component recrystallization and resultantsegregation by avoiding prolonged subjection to very high temperatures.

(a) Milling and powder recovery.-Milling of the components, tohomogeneously intermix them and obtain very fine grain sizes, is carriedout according to the practices common in the art. Optimum millingconditions will ordinarily involve a mill half-filled with a grindingmedium such as cobalt bonded tungsten carbide balls or rods, a liquidmedium such as a hydrocarbon oil, an inert atmosphere, grinding periodsof from a few days to several weeks, and powder recovery also in aninert atmosphere. The recovered powder is ordinarily dried attemperatures of around -200 C. under vacuum, followed by screening andstorage when desirable in an inert atmosphere.

(b) Consolidation.-The compositions of this invention are ordinarilyconsolidated to dense pore-free bodies by'sintering under pressure.Consolidation is ordinarily carried out by hot-pressing the mixedpowders in a graphite mold under vacuum.

When the powders are hot-pressed they are placed in the mold andinserted into the heated zone of the hot press without application ofpressure thus allowing volatile impurities to escape before thecomposition is densified. Full pressure is usually applied at or nearthe maximum temperature. 1

Maximum temperatures range between 1400 and 1900 C. depending upon theamount of intermetallic present and will ordinarily be between 1600 and1800" C. Maximum pressures range between 500 and 4000 psi. with lowerpressures being used usually in combination with lower temperatures forcompositions with a high intermetallic content. Conversely, higherpressures and temperatures are employed for compositions low inintermetallic.

As will be apparent, at higher temperatures and pressures some of thelower melting intermetallic components will tend to squeeze out of thecompositions during densification. This tendency can be used toadvantage by starting with a little more intermetallic than is desired,and operating at a high temperature and pressure. By this procedure someof the intermetallic will be squeezed out to give the desiredintermetallic content and the molten intermetallic that is eliminatedwill act as a lubricant and sintering aid during pressing. By this meansvoids can be eliminated in spite of the highly refractory nature of thefinal composition.

It is important that the composition not be heated to a temperature, orfor a period of time, which is in excess of that required to eliminateporosity and achieve density. Such higher temperatures or longer timesresult in undesirable grain growth and a resultant coarsening of thestructure, and can even result in development of secondary porosity dueto recrystallization, or in the formation of undesirable phases.

As will be demonstrated hereinafter, pressing temperatures in the rangeof 1700 to 1900 C. are usually employed for the preferred products ofthis invention and maximum temperature is applied for less than 30minutes, usually no more than 10 minutes and preferably no more thanminutes after which the product is removed from the hot zone. By theseprocedures the compositions of this invention are compacted such thatporosity is eliminated and maximum density attained without unduerecrystallization. Such products are characterized by their fine grainsize and outstanding transverse rupture strength.

The compositions of this invention, particularly those with highintermetallic content and small particle sizes, can also be densified bycold-pressing and sintering under high vacuum provided that the abovelimitation on minimum sintering time at maximum temperature is followed.It is preferred to isostatically press the powder in a sealed rubbermold suspended in water in an isostatic press capable of applying highpressures (60,000 p.s.i.) hydrostatically.

Utility The compositions of this invention can be employed ,in a varietyof types of cutting tools designed for numerous use applications. Theycan be molded or cut into standardized disposable inserts, suitable forturning, boring or milling. Or, they can be laminated with or otherwisebonded to metal-bonded carbides or tool steels for regrindable types oftooling. They are suitable generally for metal removal of ferrous metalsincluding machining or cutting hardened steels, alloy steels, maragingsteels, cast iron, cast steel, nickel, nickel-chromium alloys, nickelbased and cobalt superalloys, as well as for cutting non-metallicmaterials such as fiberglassplastic laminates and ceramic compositions.

The compositions of this invention are best suited for cutting at veryhigh speeds such metals as alloy steels (800 surface feet per minute)and cast iron (1200 surface feet per minute). This is so because of thegreat resistance to cratering and edge wear and retention of goodhardness of the compositions of this invention at elevated temperatures.Because of their good thermal shock resistance they are particularlywell suited for making repeated short cuts or other interrupted cuts inwhich the temperature of the cutting edge fluctuates rapidly.

The compositions of this invention can also be used in generalrefractory uses such as thread guides, bearings, wear-resistantmechanical parts, and as grit in resin-bonded grinding wheels and cutofiblades. In addition the compositions of this invention are useful in anyapplication where their combination of refractory properties, electricalconductivity, metallophilic nature, and thermal shock resistance offeran advantage such as in making an electrically conducting ceramic-likegrit for grinding wheels to be employed in electrolytic grinding.

The bodies of the invention are extremely resistant to oxidation at hightemperatures and this, together with their electrical conductivity,enables them to be used as furnace heating elements which can maintainhigh temperatures for long periods in oxidizing atmospheres.

This invention will be better understood by reference to the followingillustrative examples.

EXAMPLE 1 This is an example of a composition containing 50 volumepercent of titanium nitride, 25 volume percent of aluminum nitride and25 volume percent of nickel aluminide.

The titanium nitride to be used in the form of a very finely dividedpowder with a specific surface area of 3.6 m. /g. as measured bynitrogen adsorption using the Brunauer, Emmett, Teller method. Chemicalanalysis shows the powder to contain 21.40% nitrogen, 77.4% titanium,0.07% chloride, and 0.007% iron.

The aluminum nitride to be used is in the form of a finely dividedpowder with a specific surface area of 5.4 mF/g. as measured by nitrogenadsorption. Chemical analysis shows the powder to contain 31.43%nitrogen, 64.94% aluminum, 0.075% carbon, and 0.15% iron. Examination byX-ray shows it to consist of 99% AlN of an average crystallite size of197 mp as measured by X- ray line broadening, and 1% A1 0 The nickelaluminide to be used has such a particle size that it all passes througha 325 mesh screen. The specific surface area of the powder is 0.3 mP/g.as determined by nitrogen adsorption. This specific surface areacorresponds to particles of nickel aluminide of about 3.4 micronsaverage particle diameter. The oxygen content is 0.5%.

The powders are milled by loading 4290 grams of preconditionedcylindrical cobalt-bonded tungsten carbide inserts, inch long and inchin diameter, into a 1.3 liter steel rolling mill about 6 inches indiameter, also charged with 350 ml. of Soltrol 130 (saturated paraffinichydrocarbon, approximate boiling point 175 C.). The mil is then chargedwith 81.4 grams of the titanium nitride powder, 24.45 grams of thealuminum nitride powder, and 44.2 grams of the nickel aluminide powder,all as above described.

The mill is sealed and rotated at rpm. for 5 days. The mill is thenopened and the contents emptied while keeping the milling insertsinside. The mill is rinsed out with Soltrol 130 several times until allof the milled solids are removed.

The milled powder is transferred to a vacuum evaporator, and the excesshydrocarbon is decanted off after the suspended material has settled.The wet residual cake is then dried under vacuum with the application ofheat until the temperature within the evaporator is between 200 and 300C., and the pressure is less than about 0.1 millimeter of mercury.Thereafter the powder is handled entirely in the absence of air.

The dry powder is passed through a 70 mesh screen in a nitrogenatmosphere and stored under nitrogen in sealed plastic containers.

A consolidated billet is prepared from this powder by hot pressing thepowder in a cylindrical graphite mold having a squared cavity with inchcross-section and fitted with opposing close-fitting pistons. One pistonis held in place in one end of the mold cavity while 7.5 grams of thepowder is dropped into the cavity under nitrogen and evenly distributedby rotating the mold and tapping it lightly on the side. The upperpiston is then put in place under hand pressure. The assembled mold andcontents are then placed in a vacuum chamber of a vacuum hot press, themold is held in a vertical position, and the pistons extending above andbelow are engaged between opposing graphite rams of the press underpressure of about to 200 p.s.i. Within a period of a minute the mold israised into the hot zone of the furnace at 1000 C. and at once thefurnace temperature is increased while the positions of the rams arelocked so as to prevent further movement during the heatup period. Thetemperature is raised from 1000 to 1700 C. in 10 minutes. Thetemperature of the mold is held at 1700 C. for another 2 minutes toinsure uniform heating of the sample. A pressure of 4000 p.s.i. is thenapplied through the pistons for six minutes. Immediately after pressing,the mold and contents, still being held between the opposing rams, ismoved out of the furnace into a cool zone where the mold and contentsare cooled to dull red heat in about 5 minutes.

The mold and contents are then removed from the vacuum furnace and thebillet is removed from the mold and sand blasted to remove any adheringcarbon.

The hot pressed composition is nonporous, having no visible porosityunder l000 magnification.

The billet, which is a square with inch cross-section and about 0.30inch in thickness, is cut and finished as a cutting tip to exactdimensions, /2. inch x /2 inch x inch and the corners are finished witha %2 inch radius, a style known in the industry as SNG-432. This tip isused for indentation hardness test. The hardness is 91.8 on the RockwellA scale. The tip is also employed asa single tooth in a 6 inch diametermilling cutter to face mill dry and on center bars 2 inches wide of AiSi4340 steel (R 36) at a surface speed of 1000 feet per minute and a feedrate of 0.0060 inch per tooth with a'depth of cut of 0.050 inch.

Milling is continuedunder these conditions for 178 inches of bar lengthwithout wearing out.

Under these same conditions commercially available alumina cutting toolswill not cut at all and commercially available carbide tools will cutless than 40-45 inches of bar length per tooth beforecor'nplete'failure.

The same tip is employed as a cutting tool in a high speed turning teston 'AISI 1045 steel (170 BHN). The speed is 900 surface feet per minute,the feed is 0.005 inch per revolution, the depth of cut is 0.050 inch.Uniform flank wear as measured after minutes of dry turning is only0.008 inch.

Under the same conditions a Co-bonded WC-TaC-Tic commercial tool showed0.015 inch uniform flank wear after five minutes.

EXAMPLE 2 The procedure of Example 1 is repeated, except that molybdenumaluminide (Mo Al) is used instead of nickel aluminide. The componentsare used in amounts to give a compositions containing 50 volume percenttitanium nitride, 25 volume percent aluminum nitride, and 25 volumepercent molybdenum aluminide.

The molybdenum aluminide to be used has such a particle size that it allpasses through a 325 mesh screen. Thespecific surface area of thispowder is 0.2 m. /g. as determined by nitrogen adsorption. This specificsurface area corresponds to particles of molbdenum aluminide of about 2to3 microns average particle diameter, The oxygen content is 0.11%.

A cutting tip prepared as in Example 1 from this hot pressed compositionperforms very well as a cutting tip for metal cutting by milling andturning in tests similar tothose of Example 1.

EXAMPLE 3 The procedure of Example 1 is repeated except that titaniumaluminide (TiAl) is used instead of nickel aluminide. The components areused in amounts to give a composition containing 50 volume percenttitanium nitride, 25 volume percent aluminum nitride, and 25 volumepercent titanium aluminide.

The titanium aluminide tobe used has such a particle size that it allpasses through a 325 mesh screen. The crystallite size as measuredby'the X-ray diffraction line broadening method is 64 millimicrons.X-rays also show the presence of some Fe Ti and free Ti metal asimpurities. Analysis by emission spectroscopy shows that titanium is the'maor component of the powder. Other elements detected by emissionspectroscopy are aluminum 3-15%; iron 1-5%; magnesium 0.2-1%; chromium0.10.5%;

silicon 0.10.5%; calcium 500-2500 parts per million (p.p.m.); antimony200-1000 p.p.m.; lead 20-1000; manganese 10-50 p.p.m.; copper 10-50p.p.m.; sodium 10-50 p.p.m.

A cutting tip prepared as in Example'l from the hot pressed compositionof this example performs very well as a cutting tip for metal cutting bymilling and turning in tests similar to those of Example 1.

EXAMPLES 4-10 The following examples were carried out using the rawmaterials and procedures described in Example 1 except as otherwisenoted. The raw materials used in'the following examples, other thantitanium nitride, aluminum nitride and nickel aluminide arecharacterized as follows:

(A') Zirconium carbide-Materials for Industry, Inc., finezirconiunicarbide powder with a specific surface area of 0.5 square meters pergram and an oxygen content of 0.18%. Y

-,(B) Tantalum nitride--Varlacoid Chemical Co., fine 10 powder minus 325mesh with a specific surface area of 0.43 m. g. and an oxygen content of0.43%.

(C) Niobium nitride-'Cerac, Inc., fine powder minus 325 mesh with aspecific surface area of 0.18 m. g. Oxygen content of this powder is0.3%, carbon content 0.86%, and nitrogen content 11.56%. When observedunder the electron microscope the powder shows dense particles betweenland 5 microns in size, with most of the particles around 4 microns insize.

'(D) Titanium carbide--TAM Division of the National Lead Co., finetitanium carbide powder with a specific surface area of2.5 m. g.Analysis of this powder shows that total carbon content is 19.4%; freecarbon is 0.12%; oxygen content is 0.42%.

(E) Zirconium nitride-Cerac, Inc. minus 325 mesh zirconium nitridepowder characterized by X-ray as pure ZrN. Compositions containing thispowder should be handled with special care, since very fine ZrN ishighly pyrophoric and may react explosively.

(F) Titanium oxideMaterials for Industry fine titanium oxide powdercharacterized by X-ray examination as pure "H0 and has a specificsurface area of 8.8 m. /g. Examination of a dry mount specimen in theelectron microscope shows particles of around 250 millimicrons forminglarger aggregates.

(G) Zirconium oxideZircoa AHC 1.3 micron average particle size zirconiumoxide powder characterized by X- ray examination as pure ZrO and has aspecific surface area of 1.0 m.2/ g. Chemical analysis shows that thepowder contains 0.1% CaO.

(A) 4000 grams of cobalt-bonded tungsten carbide inserts are used in a.1.3 liter steel mill with 375 ml. of Soltrol oil.

(B) 14,000 grams of cobalt-bonded tungsten carbide inserts are used in aone gallon steel mill with 814 ml. of Soltrol oil.

(C) 600 grams of cobalt-bonded tungsten carbide inserts are used in a1.3 liter steel mill with '375 ml. of Soltrol oil.

The pressing cycle designated I, II and III in Table I corresponds tothe general conditions of Example 1 with the-following provisions:

(I) The sample and mold are inserted into the hot zone at a temperatureof 1500 C.

(II) The sample and mold are inserted into the hot zone at a temperatureof 1175 C.,

(III) The sample and mold are inserted into the hot.

zone at a temperature of 1000 C.

The metal cutting tests designated 1 and 2 in Table I correspond to thegeneral conditions of the cutting tests in Example 1 with the followingprovisions:

(1) High Speed Turning Test on AISI 1045 steel (Brinell Hardness Numberof 183). The speed is 900 surface feet per minute (s.f.m.); the feed is0.005 inch per revolution (i.p.r.); the' depth of cut is 0.050 inch; andthere is a negative rake. Uniform and local flank wear is measured after10 minutes of dry turning.

(2) Single Tooth Face Milling Test on A181 4340 steel (Rockwell CHardness of 36). A 6 inch milling head is used; the work is on center;dry; speed is 1-000 s.f.m.; the feed is 0.60- i.p.r.; the depth of cutis 0.050, the width of 'cut 2 inches; and there is negative rake. Toollife is measured in length of cut in inches.

TABLE I Preparation and fabrication Metal cutting test Powdercomposition Hot press cycle Type Metalline Wear resistant and maximum ofphase phase Intermetallic Milling temperature, 0. test PerformanceExample 4:

Volume percent 60 TiN AlN 30 MM 1 Good Grams 320.22 35.32 195.30 B II 1,700 2 Excelient Weight percent 59.0 6.00 35.0 EXaVmIlIe 5: t 25 Z O 60JUN M Al 0 ume percen .1 r 03 Grams 50.36 58.67 46.03 C I 1, s00{ giggWeight percent- 38.1 29.2 Exa'gnlle 6: t 55 T N Z N N'Al o ume percen ar 1 Grams 232.96 42.62 44.32 A n 1,700 g 3%?- Weight percent- 72.8 13.313.85 Exagplle 7: t 55 TN 20 AlN 5T'O 20 T111 0 111110 percen l l g 1Grams 95.51 20.85 6.80 A III 1, 500 gg Weight percent- 77.65 16.95 5.53Example 8:

Volume percent 55 NbN 20 ZXOQ 25 T3111; 1 Good Grams 147.21 35.7 11151 AI 1,300{ 2 v 0d Weight percent 49.9 12.1 37.8 g0 Exaklrlllle 9: t 55 TC40 AlN 5 N' Ti 0 ume percen 1 1 Grams 86.62 41.43 12.75 A III 1, 500gfifi Weight percent 61.43 29.48 9.04 Example 10:

Volume percent 60 TiN 35 AlN 5 MONi| 1 Good Grams 103.46 36.22 14.23 AII 1, 300 2 150 Weight percent. 67.18 23.52 9.27

I claim: 6. The refractory composition of claim 1 wherein 1. A denserefractory composition consistlng the volume percent of metalline rangesfrom to 60.

essentially of:

(1) 10 to 80 volume percent of a wear-resistant material selected fromthe group consiting of:

(a) aluminum nitride;

(b) tantalum nitride;

(c) mixtures of aluminum nitride and tantalum nitride; and

(d) a refractory oxide of an element selected from the group consistingof magnesium, zirconium, hafnium, titanium, chromium, beryllium, zinc,calcium, thorium, barium, strontium, silicon, the rare earth metals, andmixtures thereof;

(2) 15 to 8 0 volume percent of a metalline selected from the groupconsisting of titanium carbide, titantalum carbide, niobium carbide,niobium nitride, tanium nitride, zirconium carbide, zirconium nitride,and mixtures thereof; and

(3) 5 to volume percent of an intermetallic selected from the groupconsisting of molybdenum nickelide, tantalum nickelide, zirconiumnickelide, niobium nickelide, cobalt aluminide, cobalt titanide, ironaluminide, iron titanide, nickel aluminide, nickel titanide, tungstenaluminide, molybdenum aluminide, niobium aluminide, tantalum aluminide,titanium aluminide, zirconium aluminide, and mixtures thereof;

the composition having the further limitations that:

(A) the average grain size is smaller than 10 microns;

*(B) the composition is composed of two interpenetratingthree-dimensional networks, one network consisting essentially of thewear-resistant material and the other network consisting essentially ofthe metalline and the intermetallic; and

(C) the volume percent of the metalline must not be less than the volumepercent of the intermetallic.

2. The refractory composition of claim 1 wherein the volume percent ofwear-resistant material ranges from 10 to 50.

3. The refractory composition of claim 2 wherein the volume percent ofwear-resistant material ranges from 15 to 30.

4. The refractory composition of claim 1 wherein the wear-resistantmaterial is selected from the group consisting of aluminum nitride,tantalum nitride, or mixtures thereof.

5. The refractory composition of claim 4 wherein the wear-resistantmaterial is aluminum nitride.

7. The refractory composition of claim 6 wherein the volume percent ofmetalline ranges from 45 to 55.

8. The refractory composition of claim 1 wherein the metalline isselected from the group consisting of titanium nitride, zirconiumnitride, niobium nitride, and mixtures thereof.

9. The refractory composition of claim 8 wherein the metalline istitanium nitride.

10. The refractory of claim 1 wherein the volume percent ofintermetallic ranges from 15 to 30.

11. The refractory composition of claim 10 wherein the volume percent ofintermetallic ranges from 20 to 30.

12. The refractory composition of claim 1 wherein the intermetallic isselected from the group consisting of molybdenum nickelide, cobaltaluminide, iron aluminide, nickel aluminide, and mixtures thereof.

13. The refractory composition of claim 1 wherein the average grain sizeis less than 5 microns.

14. A dense refractory composition consisting essentially of:

(1) 15 to 30 volume percent of aluminum nitride;

(2) 45 to 55 volume percent of titanium nitride; and

(3) 20 to 30 volume percent of an intermetallic selected from the groupconsisting of molybdenum nickelide, cobalt aluminide, iron aluminide,nickel aluminide, and mixtures thereof;

the composition having the further limitations that:

(A) the average grain size is less than 5 microns and (B) thecomposition is composed of two interpenetrating three-dimensionalnetworks consisting essentially of the wear-resistant material and theother network consisting essentially of the metalline and theintermetallic.

References Cited UNITED STATES PATENTS 3,108,887 10/1963 Lenie et al.106-65 3,236,663 2/1966 Grulke et a1. 1 06-65 3,251,700 5/1966 Mandorf106-65 3,256,103 6/1966 Roche et al. 106-55 3,261,701 7/1966 Grulke106-65 3,408,312 10/1968 Richards et al. 106-65 JAMES E. POER, PrimaryExaminer US. Cl. XR.

mg v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 37 Dated y 97 Inventor(s) Paul C. Yates It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 11 Lines 43/ 4 4 read "tantalum carbide, niobium carbide, niobiumnitride,

tanium nitride, zirconium carbide, zirconium nitride,"

it should read --tanium nitride, zirconium carbide, zirconium nitride,tantalum carbide, niobium carbide, niobium nitride,--

Signed and sealed this 6th day of February 1973.

(SEAL) Attest:

ROBERT GOT'I'SCHALK Commissioner of Patents EDWARD M.FLETCHER,JR.Attesting Officer

